Field
The present invention relates to a semiconductor device capable of improving the moisture resistance without increasing the thickness of the insulating film and a method for manufacturing the same.
Background
In a conventional device, a metal-insulator-semiconductor (MIS) is formed by inserting an insulating film between a gate electrode and a semiconductor in order to obtain improvements in withstand voltage and current collapse (see, for example, JP 2013-115323A). A device is also known in which a barrier layer formed of an oxide and a nitride is deposited between a gate metal constituted of Au and an SiN insulating film in order to obtain an improvement in reliability (see, for example, JP 2012-175089A).
In conventional GaN-HEMT transistors for radiofrequency devices, SiN (silicon nitride) is ordinarily used as a surface protective film to limit trapping between a semiconductor surface and the surface protective film for protecting the semiconductor surface. Also, an SiN moisture-resistant film is formed so as to cover a portion around the gate and the surface protective film. The moisture resistance cannot be improved unless the film thickness of the SiN moisture-resistant film is increased. With increase in film thickness, however, the capacitance increases, resulting in a degradation in RF characteristic.